Page 36 - Delaware Medical Journal - September/October 2020

METHODOLOGY
A retrospective study identified a
total of 8,240 patients diagnosed with non-small cell lung cancer during the period of 1999-2015 with approval of the Institutional Review Board (IRB) at ChristianaCare. Of these, 45 patients had tumors measuring 1cm or less by pathologic evaluation. Data points collected included patient sex and
age, use of PET scan, type of surgical resection, stage, overall survival, and disease-free survival. Patients with sub-centimeter lung cancers were also consented for peripheral blood-sample collection and bioanalysis through an IRB-approved protocol in conjunction with the Wistar Cancer Institute.
RESULTS
There were 19 male and 26 female patients with a median age of 64 years at the time of cancer diagnosis. There were 21 patients who underwent open thoracotomy versus 24 who had a video-assisted thoracoscopic surgery (VATS) procedure. There were 14 patients who underwent lobectomy versus 31 who had a wedge resection and 17 patients also underwent a mediastinal lymph node dissection. The 30-day operative mortality was 0%. All patients were diagnosed with adenocarcinoma or squamous cell. All patients were stage IA and no patients received adjuvant chemotherapy or radiation therapy. This cohort was then divided into three subgroups based on the size of the lung lesion (Table 1).
DISCUSSION
The size of a pulmonary nodule is one of the most important prognostic
factors when assessing for the risk
of malignancy. Many guidelines
use size as the determining factor
for the management and follow-up
of small pulmonary nodules. The Fleischner Society guidelines use
6mm as a cutoff when determining a nodule’s significance. The incidence
of malignancy in nodules at this size
or less is very low, at 0.5% based on Trial. These guidelines also suggest 8mm as a threshold for when to consider invasive testing.3 The question remains whether finding and treating sub-centimeter lung cancers results
in any significant survival benefit
for patients. Based on the data above, the recurrence-free survival was not significantly different when analyzing three size groups of 1cm and under (Table 1).
We also looked at a number of variables and assessed their effect on survival. The extent of surgical resection, lobectomy vs. wedge, as well as lymph- node dissection, appeared to affect survival (Figure 1). Formal lobectomy and lymph-node dissection is the gold standard for lung cancer treatment
and has been shown to be superior to
a non-anatomic wedge resection. The differences we found may have been related to patient selection though, as patients with higher comorbidities are more likely to have undergone a limited resection and not have had a lymph- node dissection (Figure 1).
As might be expected, the utility of PET scans for distinguishing malignant from benign was low for lung cancers less than 1cm in this study. This is in accordance with recommendations from the American College of Chest Physicians and the French Thoracic Society, which do not recommend PET scans for nodules less than 8mm or
less than 10mm, respectively.4 In our study, of the 10 patients who had a pre-operative PET scan and a sub- centimeter lung cancer, only one had positive uptake, which is represented by an SUV (standard uptake value)
of 2 or higher. Of the eight patients who had a PET scan and a lung cancer measuring 1cm in size, six had a positive PET result. Thus, a cutoff of 1cm appears to be appropriate when deciding whether or not to obtain a pre-operative PET scan. Of note, of the 10 patients with sub-centimeter lung cancers and pre-operative PET scans, two had recurrences and one of these two patients had the highest SUV seen in this group. Of the eight patients with 1cm lung cancers and PET scans, there were three recurrences, and two of
the three had the highest SUV values within this group. This suggests that a higher SUV is associated with a higher recurrence rate. This has been shown in previous studies, although not in cancers at these small sizes.5
A collaboration between the Helen F. Graham Cancer Center & Research Institute and the Wistar Cancer Institute has been ongoing since
2011 and has led to the development
of a blood test that can distinguish malignant from benign nodules.6 This test, recently published in Cancer Research,6 consists of a 41 biomarker a 2.5ml peripheral blood sample. The biomarker assay ref lects changes in gene expression that differ between patients with benign or malignant lung nodules. The test results in a sensitivity of 90% and a specificity of 40%
when used to determine malignancy in 6mm-14mm nodules. This test outperformed other pulmonary nodule risk calculators such as the Mayo Clinic, Brock University, and Veteran Administration models.7 Looking just
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Del Med J | September/October 2020 | Vol. 92 | No. 5